Suede-like sheet material of styrene/butadiene polymer containing an additive

ABSTRACT

AN IMPROVED SUPPLE, SYNTHETIC, MICROPOROUS VAPOR PERMEABLE SUEDE-LIKE SHEET MATERIAL OF A NON-WOVEN SYNTHETIC FLEXIBLE FIBROUS WEB THAT IS IMPREGNATED WITH A POLYMERIC BINDER OF STYRENE AND BUTADIENE AND THE POLYMERIC BINDER CONTAINS ABOUT 0.1-10 PARTS IF A SILICONE OIL ADDITIVE PER 100 PARTS OF POLYMERIC.

United States Patent Olfice Patented May 11, 1971 ABSTRACT OF THEDISCLOSURE An improved supple, synthetic, michoporous vapor permeablesuede-like sheet material of a non-woven synthetic flexible fibrous webthat is impregnated with a polymeric binder of styrene and butadiene andthe polymeric binder contains about 0.1- parts of a silicone oiladditive per 100 parts of polymeric.

BACKGROUND OF THE INVENTION This invention relates to a novel suede-likemicroporous sheet material and in particular to a synthetic suede-likemicroporous vapor permeable sheet material that has a substantiallyimproved nap over prior art synthetic suede products.

Leather-like sheet materials that can be formed into a suede-like sheetmaterial have been prepared by a variety of processes as disclosed inthe following patents: Graham et al. US. 2,715,588, issued Aug. 16,1955; Gaylord U.S. 2,917,405, issued Dec. 15, 1959; Proctor US.2,994,617, issued Aug. 1, 1961; Hollowell patents, U.S. 3,067.482 and3,067,483, both issued Dec. 11, 1962; British Pat. 986,437, publishedMar. 17, 1965 and FitzGerald et al. US. 3,228,786, issued J an. 11,1966. These sheet materials have a very wide variety of uses from shoeuppers to apparel suede. However, While these materials have beenconsidered acceptable suede-like materials after buffing, the surface ofthe material does not approach that of a natural leather suede asclosely as is desired. The density and fiber length of the fibers thatform the suede-like surface of these prior art products are insufficientto form a product which very closely resembles a natural leather suede.

A synthetic material that would closely resemble natural leather could'be used as an apparel suede, a brushed casual shoe upper, as afelt-like mens hat material and the like.

The novel suede-like product of this invention surprisingly has asurface which more closely approaches that of natural suede leather thanthe aforementioned prior art products which are of a high quality andare excellent for many purposes. Along with this improved property, thenovel product of this invention still is highly flexible, soft, suppleand has a high water vapor permability. This is accomplished by using aparticular additive with the polymeric binder used to form the sheetthat will give a nap on the novel product with a high fiber density anda greater fiber length than previously has been possible with prior artproducts.

SUMMARY OF THE INVENTION The supple synthetic microporous vaporpermeable suede-like sheet material comprises:

(a) a non-woven synthetic flexible fibrous web that is impregnated (b) apolymeric binder which consists essentially of a polymer of styrene andbutadiene and contains 0.1- 20 parts of a nap improving additive per 100parts of polymeric binder which is a silicone oil which has a viscosityat 25 C. of at least 10 centistokes;

wherein said microporous sheet material has a water vapor permeabilityvalue of at least 1000 grams of water/100 square meters/hours and abinder to fiber ratio of about 0.2-3.0.

DESCRIPTION OF THE INVENTION The novel sheet material of this inventionis prepared by forming a non-woven porous substrate or -web,impregnating this web with a polymeric binder, and coagulating thispolymeric binder, preferably into a microporous form. The non-woven webis impregnated with sufficient polymeric binder to give the finalproduct a binder/fiber ratio of about 0.2-3.0. For best results, abinder/fiber ratio of 0.5- 2 is preferred.

The term micrporous refers to a porous material in which the individualpores are not discernible to the naked eye.

Preferably, the novel sheet material of this invention has a fiexuralrigidity at a -mil sheet thickness of about 1,000-80,000milligrams-centimeters, and more preferably, 4,000-30,000milligrams-centimeters, measured according to the method ofASTM-1388D64. A sheet having the fiexural rigidity within the aboveranges indicates that the sheet is supple and flexible and not stiff andboard-like.

Water vapor permeability of the novel sheet material of this inventionis determined by sealing the sheet on top of a cup containing CaCl Thissealed cup is stored at relative humidity at 72 F. and the weightincrease of the cup due to moisture permeating through the material isdetermined and the water vapor permeability value of the sheet iscalculated in Preferably, the novel sheet material of this invention hasa water vapor permeability of 2,00015,000 grams/ square meters/hour.

The non-woven porous fibrous substrate or web used to form the novelsheet material of this invention preferably has a density of about0.011.0 gram per cubic centimeter (gm./cc.), and more preferably, about0.1-0.4 gm./cc. The method used to prepare the non-woven web and thefibers from which the web is prepared are not critical.

Generally, the non-woven web is prepared by forming fibers into a loosebatt by any known method, such as carding, blowing the fibers, droppingthe fibers and the like. Preferably, a batt of about 4-20 ounches persquare yard is formed by air-blowing the fibers. The batt is thencompacted by any of the well-known techniques, such as mechanicalneedling. Preferably, the resulting web is further compacted by heatshrinking, for example, which can be accomplished by immersion in hotwater. A web having properties of stretchability or shrinkabilitybalanced in each direction is formed by cross-lapping the fibers intolayers of dissimilar orientation within the plane of the Web. Whenunidirectional stretchability or shrinkability is preferred, thecrosslapping is omitted and most of the fibers are laid so that theyhave a similar orientation to the plane of the web.

The choice of the particular fibers from which the substrate used inthis invention is made is not critical; for example, fibers ofpolyamides, polyesters, polyesterimides, polyurethanes, chain-extendedpolyurethanes, acrylic pol ymers, acetate polymers, viscose rayon, glassand mixtures thereof, can be used. Elastomeric fibers can be used toform the web or can be blended with any of the aforementioned webs.

One particularly preferred non-woven substrate used to form the novelproduct of this invention which gives a high quality suede-like materialis a non-woven web of needled, heat shrunk about 1-2 denier polyethyleneterephthalate fibers having a density of about 0.15-0.30 gm./cc.

A non-woven porous fibrous substrate that is impregnated with apolymeric material that has a binder to fiber ratio of less than 1.0 canalso be used as a substrate to form the novel product of this invention.This substrate is reimpregnated with sufficient polymeric binder to givea product with a final binder/fiber ratio of less than 3, preferably1-2. After impregnation, the polymer is coagulated in a microporousform. One preferred substrate of this type is a non-woven needled heatshrunk batt of polyethylene terephthalate fibers that has beenimpregnated with a mixture containing up to 50% by weight polyvinylchloride and at least 50% by weight of a chainextended polyurethanepolymer. One preferred polyurethane is the reaction product of anaromatic diisocyanate and po1y(alkyleneether) glycol which ischainextended with a diamine that has at least one active hydrogenattached to each nitrogen atom.

The styrene/butadiene polymeric binder used to impregnate the non-wovenfibrous substrate to form the novel sheet material of this inventionshould be tough and durable, and preferably, should form a microporousstructure. These characteristics are necessary to form a product whichis a suede leather replacement for shoe uppers, for wearing apparel,such as hats, coats, vests and the like. Styrene/butadiene polymers thatform sheet materials that have these desired characteristics preferablycontain 25-50% by weight styrene and 75-50% by weight butadiene andgenerally have a tensile stress at 5% elongation of about 4-150 p.s.i.,and preferably 8-72 p.s.i.

Tensile stress at 5% elongation is the force in pounds which is requiredto elongate a sample 5% divided by the cross-section are of the samplewith the results being expressed in pounds per square inch (p.s.i.).Preferably, an 8-12 mil thick film is prepared from the styrene/butadiene polymer used to prepare the novel sheet material of thisinvention. Test samples of about /2 inch by 4 inches are cut,conditioned at 5 relative humidity and tested at 23 C. The samples aretested at the above temperature and humidity conditions on an Instrontensile tester using about 1 inch between grips on the sample, across-head speed of 1 inch per minute and a chart speed of 10 inches perminute.

One preferred styrene/butadiene polymeric binder used to prepare thenovel sheet material of this invention contains in addition to styreneand butadiene about 0.1% by weight of an a,B-ethylenically unsaturatedcarboxylic acid. One particularly preferred binder of this type whichprovides excellent adhesion to the non-Woven substrate and is readilycured by conventional techniques consists essentially of 25-50% byweight styrene, 75-50% by weight butadiene and 0.1-5 by Weight of one ofthe following carboxylic acids; acrylic acid, methacrylic acid oritaconic acid.

The above styrene/butadiene polymeric binder can be in a solution or adispersion to impregnate the non-woven substrate to form the novel sheetmaterial of this invention. Preferably, dispersions of the above polymereither using an organic or an aqueous phase as the dispersing medium areused to impregnate the non-woven substrate to form the novel sheetmaterial of this invention. Dispersions can readily be formed thatcontain a high polymer solids content but have a low viscosity and arereadily adaptable to an impregnation process. Aqueous dispersions orlatices of the above styrene/butadiene polymeric binders areparticularly preferred since there are no problems such as occur withsolvent dispersions, such as the high cost of solvents which requiresolvent recovery. Moreover, latices are readily coagulated afterimpregnating the non-woven substrate by heat or cold or by chemicalsinto a microporous structure.

Preferably, for best results, the latex of the styrene/ butadienepolymeric binder used in this invention has a low viscosity of l-300centipoises and a polymer solids content of about 20-70% by weight andmore preferably, a 40-60% polymer solids content is used,

To give a novel suede-like sheet material of this invention a dense napwith long fibers, an additive of silicone oil is added to the polymericbinder in an amount of 01-20 parts of additive per parts of polymericbinder. For best results, about 1-15 parts of additive per 100 parts ofbinder are used.

The silicone oils that are useful additives in this invention are of theformula Si (R) odwhere R is an alkyl group of 1-4 carbon atoms or aphenyl group or a mixture of alkyl and phenyl groups, and the oil has akinematic viscosity at 25 C. of at least 10 centistokes and may have aviscosity up to 2.5)(10 centistokes. Preferably, the oil has a kinematicviscosity of 5030,000 centistokes. The aforementioned R group can bemethyl, ethyl, propyl, isopropyl butyl, isobutyl or phenyl. Onepreferred silicone oil, since it gives a high quality product, ispolydimethylsiloxane which has a kinematic viscosity at 25 C. of about20-100 centistokes.

Often it is desirable to add pigments, extender pigments and dyes to thebinder used to form the novel sheet material of this invention to givethe product the desired color. About 01-20% by weight pigment, based onthe weight of the polymeric in binder, and preferably, 2-10% by weightcan be used. Typically useful pigments are, for example, metal oxides,such as titanium dioxide, zinc oxide, metal hydroxides, chromates,silicates", sulfides, sulfates, carbonates, carbon blacks, organic dyes,such as ,B-copper phthalocyanine, lakes and metal fiake pigments, ferricyellow (yellow iron oxide pigment), burnt sienna, (an orange brownmineral pigment containing iron oxide, manganese dioxide and clay) andthe like.

Thickening agents can be added to a latex used in this invention toprepare the novel product to give the desirable impregnating viscosity.The useful viscosity range for the latices used to form the novel sheetmaterial of this invention is about 1 to 300 centipoises (cps.) with thepreferred range being about 10 to 100 (cps). Thickening agents mostcommonly used are ammonium caseinate, ammonium alginate, methylcellulose (25 cps. to 50,000 cps. viscosity, measured as a 2% aqueoussolution at 25 C.) and "sodium polyacrylate. Other thickening agents,such as polyacrylio acids, polyvinyl alcohol, carboxymethyl celluose,polyvinyl pyrrolidone, maleic acid copolymers, gelatine, and the like,can also be used. It is desirable, but not absolutely necessary, toremove the thickener from the latex after it has been coagulated; thisis accomplished by washing the coagulated latex with water. If thethickener is retained in the sheet, subsequent rewetting of the materialcauses the thickener to come to the surface and makes the material feelslimy. This washing step may be eliminated from the process bycross-linking and insolubilizing the thickener and can be accomplishedby adding a crosslinking agent such as polyacrylamide and an agent whichinsolubilizes the thickener, such as bis-hydroxy methyl urea. Thesubsequent drying and curing of the polymer after coagulation at anelevated temperature aids in the cross-linking and insolubilization ofthe thickener.

Antioxidants are generally added in small amounts to the latex used inthis invention of unsaturated polymers, such as4,4-butylidene-bis-(6-tertiary-butyl-m-Cresol), 2,2'-methylene-bis-4-methyl-G-tertiary-butylphenol4,4'-thio-bis-(6-tertiary-butyl-m-cresol) and the like.

Plasticizers may be added in small amounts to the latex to form thenovel sheet material of this invention. The type of plasticizer used isdependent on the latex polymer.

Curing agents are generally added in small amounts to the latex used toform the novel sheet material of this invention, such as zinc oxide;sulfur plus an accelerator like zinc dibutyl dithiocarbamate;melamine-formaldehyde polymer; phenolformaldehyde polymer. Curing orvulcanization of the latex polymer after it is coagulated in thenon-woven substrate is carried out at about 100160 C. and preferably, at1l0150 C.

If the latex is coagulated by heat, generally heat sensitizers, such aspolyvinylmethylether, ammonium sulfate, zinc ammonium acetate,methylcellulose and the like, are added. Heat coagulation can beaccomplished by hot air, steam, microwace, infrared heat and the like. Atemperature of about 40100 C. is usually required with the preferredtemperature range being about 60-90 C.

If the latex is coagulated by chemical means, the impregnated sheet isimmersed in a liquid, for example, an acetic acid bath containing about1 to 10% by weight acid. Solutions of the following can be used tocoagulate the latex: calcium chloride, barium chloride, zinc acetate,formic acid, aluminum sulfate and the like.

Preferably, after the non-woven web is impregnated with the latex, thelatex is coagulated by freezing the latex at about C. to 100 C. forabout 10 minutes to 2 hours. After coagulation, the novel sheet materialis dried, preferably at a temperature of about 30150 C. However, it ispossible to dry the product at a lower temperature, for example, roomtemperature about 22 C.

If a colored product is desired, the novel sheet material of thisinvention can be dyed by ordinary techniques after the polymer has beencoagulated. Manwaring US. Pat. 3,337,289, issued Aug. 22, 1967, teachesa dyeing process that can be used on the novel product of thisinvention. Preferably, the non-woven is dyed and then a coloredpolymeric binder is used to form the novel sheet material of thisinvention. The binder is colored as aforementioned by the addition ofdyes or pigments.

Printing, stencilling embossing, preferential dyeing, and other knowntechniques for surface decoration can be used to modify the novelproduct of this invention.

When a denser product is wanted, the dried sheet is pressed between twosmooth heated surfaces. The time temperature and pressure of pressingare controlled to maintain product permeability and suppleness, as willbe apparent to those skilled in the art.

The suede surface of the novel sheet material of this invention isformed by raising a nap on one or both sides of the smooth, supplemicroporous sheet in any suitable manner known in the art of nappingfabrics and tanned skins. A preferred napping process involves buffingwith emery covered rolls followed by brushing. Buffing also improved thesuppleness of the product besides softening its surface feel.

Another optional feature is to treat the novel product with known fabricsofteners, or to likewise treat the mat at any stage of the process.

In general, the product of this invention is a versatile material withmany uses. The novel product of this invention, because of its desirableproperties, may be buffed on one side and coated on the other, forexample, coated with a microporous layer.

6 The following examples illustrate the invention. All parts andpercentages are by weight unless otherwise specified.

EXAMPLE 1 Latex A is formulated by blending the following ingredients:

Parts by weight A Laxtex50% solids dispersions of a carboxy modifiedpolymer of about 40% by weight styrene and about 60% by weight butadiene200.0 Zinc oxide dispersion50% zinc oxide solids 10.0 Antioxidantdispersion40% by weight aqueous dispersion of 2,2methylene-bis-(4-methyl-6-tbutyl-phenol) 2.5 Zinc dibutyldithiocarbamate dispersion-43% by weight zinc dibutyl dithiocarbamate6.0 Lampblack50% aqueous dispersion 4.0 Sulfur-50% aqueous dispersion4.0 Polypropylene glycol (average molecular weight 425)-50% aqueoussolution 37.0 Nonionic surfactant25% aqueous solution of a condensationproduct of octyl phenol and 9-10 moles of ethylene oxide 16.0 10%aqueous emulsion of silicon compound Dow Corning Antifoam B which isbelieved to be a thickened dimethyl siloxane oil that has a viscosity at25 C. of at least 20 centistokes 50.0 Ammonium sulfatel0% aqueoussolution 40.0

After the above ingredients are blended together, the pH of the latex isadjusted to 8.8 with 14% aqueous ammonia solution.

The tensile stress of a dried and cured at 120 C. non-porous polymerfilm of the latex at 5% elongation is at least 8 p.s.i., determined at23 C. and 50% RH. on a 0.5 inch wide sample on an Instron tensile testerusing 1 inch between jaws and an elongation rate of 1 inch per minute.

An 18 inch by 18 inch by A-inch web prepared by needling and heatshrinking a batt of 1.8 denier polyethylene terephthalate fibers 1.5inches in length and having a web density of about 0.2 g./cc. isimmersed in the above-prepared latex binder. The amount of latex pickedup by the web is about 350% by weight. This impregnated web is thenwrapped in aluminum foil and held 30 minutes at C. to gel the latexbinder. The web is then washed with water and cured minutes in acirculating air oven at C. The resulting product is a soft, flexiblematerial having excellent scuff resistance and excellent water vaporpermeability.

Latex B is formulated using the identical ingredients and in the sameamounts as used to formulate Latex A except the silicon oil emulsion isomitted. The latex polymer has about the same tensile stress as theLatex A polymer. The non-woven web of polyethylene terephthalate fibersdescribed above is impregnated following the above procedure.

Each of the above-prepared sheets are split to a 75 thickness and buffedon both sides to a thickness of about 6065 mils; about 3 mils are buffedfrom each surface of the sheet.

The resulting sheets have the following properties:

Latex A Latex B 1 Nap density=Low nap density indicates relatively fewfibers protruding from the buffed surface, a high nap density indicatesthat the surface is completely covered with nap.

The above results indicate that the silicone oil additive greatlyimproves the length and density of the nap without adversely affectingother properties of the sheet such as water vapor permeability.

EXAMPLE 2 A heat shrunk non-woven web of needled polyethyleneterephthalate fibers is impregnated with a chain-extended polyurethanesolution described in Example 1 of Holden US. 3,100,321, issued Aug. 13,1963, to form an impregnated sheet that is split to a thickness of about70 mils. This sheet has a binder/fiber ratio of about 0.5 and a densityof about 0.35 g./cc.

The above impregnated sheet material is reimpregnated with the Latex Abinder of Example 1.

Excess latex binder is squeezed from the sheet by a pair of nip rolls.The resulting product is dried at 110 C. Both sides of the sheet arebuffed with 120 grit sandpaper, yielding a suede-like material that issoft, supple, vapor permeable and has a long nap and dense nap and isuseful, for example, for shoe uppers.

The upper prepared polyurethane impregnated sheet is reimpregnated asabove with a Latex B that does not contain the silicone oil additive.The sheet is dried and bufied as above but the resulting material has alow nap density and a short nap length which illustrates that siliconeoil additive greatly improves nap length and nap density.

What is claimed is:

1. A supple synthetic microporous vapor permeable suede-like sheetmaterial comprising (a) a non-woven synthetic flexible fibrous webimpregnated with (b) a polymeric binder which consists essentially of apolymer of styrene and butadiene and contains a nap improving additiveabout 0.1-20 parts of additive per 100 parts of polymeric binderconsisting essentially of a silicone oil which has a kinematic viscosityat 25 C. of at least 10 centistokes; said microporous sheet materialhaving at least one suede surface, a water vapor permeability of atleast 1000 grams/100 square meters of sheet material/hour and abinder/fiber ratio of 0.2-3.0.

2. The microporous suede-like sheet material of claim 1 in which thebinder contains 1-10 parts of additive per 100 parts of polymer, thewater vapor permeability is about LOGO-15,000 grams/100 squaremeters/hour, and the binder/ fiber ratio is about 0.5-2.

3. The microporous suede-like sheet material of claim 2 in which thepolymeric binder consists essentially of 25-50% by weight styrene,75-50% by weight butadiene and 0.1-5% by weight of an u,}8-unsaturatedcarboxylic acid.

4. The microporous suede-like sheet material of claim 2 in which theadditive is a silicon oil of the formula Si R 1 L )2 OJ11 where R isselected from the group consisting of an alkyl group having l-4 carbonatoms and a phenyl group and said'silicone oil has a kinematic viscosityat 25 C. of about 50-30,000 centistokes.

5. The microporous suede-like sheet material of claim 2 in which saidnon-woven web consists essentially of polyethylene terephthalate fibers.

6. The microporous suede-like sheet material of claim 3 in which thea,,8-unsaturated carboxylic acid is selected from the group consistingof acrylic acid, methacrylic acid and itaconic acid.

7. The microporous suede-like sheet material of claim 3 in which thenon-woven web consists essentially of 8 polyethylene terephthalatefibers and in which the additive is a silicone oil of the formula{Si(CHs)2O]n and has a kenematic viscosity at 25 C. of about 20-100centistokes.

8. The microporous suede-like sheet material of claim 1 in which thenon-woven synthetic flexible fibrous web before being impregnatedcontains a binder of a polymeric material and has a binder/fiber ratioof less than 1.

9. The microporous suede-like sheet material of claim 8 in which thebinder of a polymeric material consists essentially of at least 50% 'byweight of a chain-extended polyurethane and up to 50% by weight ofpolyvinyl chloride.

10. A process for forming a supple synthetic microporous vapor permeablesuede-like material which comprises (a) impregnating a non-wovensynthetc flexible fibrous web with (b) a polymeric binder which consistsessentially of a polymer of styrene and butadiene and contains a napimproving additive about 0.1-20 parts of additive per parts of polymericbinder which consists essentially of a silicone oil which has akniematic viscosity at 25 C. of at least 10 centistokes;

(c) removing excess liquid from the Web and drying the web; and

(d) napping at least one side of the impregnated web to form asuede-like surface;

said microporous sheet material having a water vapor permeability of atleast 1000 grams/100 square meters of sheet material/hour and abinder/fiber ratio of 0.2-3.0.

11. A process for forming a supple synthetic microporous vapor permeablesuede-like sheet material which comprises the following steps:

(a) forming a microporous sheet having a binder/ fiber ratio of lessthan 1 by impregnating a nonwoven synthetic fibrous flexible web with apolymeric binder, coagulating said binder and Washing and drying saidsheet;

(b) reimpregnating the microporous sheet formed in step (a) above with alatex of a polymeric binder which consists essentially of a polymer ofstyrene and butadiene and contains a nap improving additive about 0.1-20parts of additive per 100 parts of polymeric binder which consistsessentially of a silicone oil which has a kinematic viscosity at 25 C.of at least 10 centistokes; coagulating the latex and washing and dryingsaid sheet material; and

(c) napping at least one side of the reimpregnated sheet to form asuede-like surface;

the resulting sheet material having a water vapor permeability of atleast 1000 grams/100 square meters of sheet material/hour and abinder/fiber ratio of 0.5-2.

References Cited UNITED STATES PATENTS 2,715,588 8/1955 Graham et a1162-135 3,067,482 12/1962 Hollowell 28-74 3,167,448 l/1965 Hirshfeldll7l6lX 3,400,013 9/ 1968 Harrison 117-4X ALFRED L. LEAVITT, Examiner E.G. WHITBY, Assistant Examiner US. Cl. X.R.

